Dry kiln



New. `8, 1927.

1,648,089 J. B. WELCH DRY KILN Filed Maron e. 192e 2 sheets-sheet 2 ATTORNEYS lll Patented Nov.. 8, ltl..

Unirse sra'iss terasse rarsnr oFFica.

JOHN `BERClllVANS VELCH, OF NEW GRLEANS, LOUISIANA.

DRY mmv.

Application filed March G, 1925. y Serial No. 92,810.

This invention relates to apparatus for drying lumber and other similar materials and has tor its object the provision of an improved drying apparatus. V

ln the crying ol lumber it is important to maintain the humidity and temperature ol- Sametime progressively increases from the entrance to the exit ends. When these conditions are appropriately'.maintained, the rate of drying of the lumber as it moves through the kiln will be substantially uniform, and abnormally rapid drying toward the dry end, resulting in damage to the luin-` ber, will be avoided.

ln accordance with the present invention the drying chamber, throughout its lower part7 is provided with a heating device comprising a plurality of full length passes, and a relatively short pass, of heating pipes, each of these passes being connected in series. The relatively short pass of heating pipes is located in the exit or dry end of the drying chamber which it is desired to maintain at a somewhat higher temperature than the entrance or green end. A suitable supply header extends crosswise of the chamber at a point between the two ends but nearer the discharge end, and supplies live steam directly to the relatively short pass of heating pipes. This relatively short pass is located .above the full length passes andthe steam travels through Vthe passes in series, the condensed steam flowing downwardly through the series o'l passes and escaping through a suitable drain header to whichthe bottom end ol thelast lull lengthl pass vis connected, this header being located at the dry or exit end of the kiln.

Thusthe live steamtirst venters the relatively short passes ol' heating pipes, and returns in an opposite direction through the relatively long passes of heating pipes`immediately beneath the short passes. LThe direction of the now considerably cooled steam is again reversed as it is made to flow down through the still lower long passes of heating pipes, to the discharge header at the dry end or the kiln. f

lt is thus seen that/the steam` will have given up a very substantialpart of its heat at the dryend half of the kiln, because of its initial double return flow, beforeit reaches the wet end haltet the kiln. Moreover, the gradual cooling of the steam in this manner assures a gradual transitionin the temperaturc of the kiln from a point of relatively' high heat at the extreme dry end toa point of relatively low heat at the extreme wet end of the kiln. Hence, as the lumber is made to `progressively move Jfrom the wet to the dry end of the kiln, the humidity necessarily decreases as the temperature increases.' Unw f der properly controlled conditions, this is' the endto be desired in the successful drying of lumber.

This invention will be more clearly understood by the accompanying drawings, taken` in conjunction with the following descrip tion, in which: f

Fig. l is a longitudinal section through the drying apparatus;

Fig. 2 is a horizontal section taken at a plane just above the heating device;

Fig. 3 is a sectiontaken on line 3-3 of Fig. 2 to illustrate. a `detail of this support for the heating pipes; and,

Fig. l is a similar detail line 4 4 of Fig. 2.

yReferring now to the accompanying draw-r ings, the kiln lfor lumber drying comprises an elongated chamber 5 'of concrete, wood or section taken on having the usual openingsV 6 and 7, provided with doors for the introduction and delivery of the lumber to be dried. `The lumber enters in the usual manner von appropriate trucks which run upon the rails` 8 extending throughout the length of the kiln.` These rails are supported upon transversely `extending steel beams 9 which arek'supported uponposts 10 embedded in a suitable foundation ll preferably o concrete. The steel beams 9 entend preferablyfth'e vfull width-oli the drying lchamber andare embedded in the side walls thereof` as indicated at 12.] The height oit the posts 10 from the entrance or ber.

The heating device is supported below the beams 9 and comprises the relatively short pass 13 of heating pipes which extend from the supply header 14 to the exit end ot the kiln. Supply header 14 is located intermediate the ends of the drying chamber, preferably near the center thereof, but may be placed an appropriate distance either side of the center to give the required amount of additional heat at the dry end of the chamber. kAt this point the pipes constituting pass 13 are connected b return bends 15 tothe pipes which constitute the intermediate full length passes 16. The pipes of this pass extend from the exit end through the. entire length of the kiln to the green end where they are connected by means of return bends 17 to the pipes of the last pass 18 which extend through the entire length of the kiln to the dry end and terminate in a drain header 18.

Steam under appropriate pressure is supplied to the header 14 through pipe 19 in which there is located a controlling valve 20 which may be operated either manually or automatically by vmeans of temperature variations within the drying chamber. The condensed steam collecting in drain header 18 passes out through a discharge pipe 21 in which there is preferably placed an appropriate. steam trap (not shown) for the purpose of preventing the wastage of steam. Live steam is also supplied through pipes 22 to transverse .steam spray pipes 23 provided with jets for directing the steam spray preferably toward the dry end of the kiln to facilitate circulation.

In the operation of the kiln the lumber enters at the opening 6 passing in the direction of the arrow progressively through the kiln and emerging eventually through the opening 7 at the dry end,rsteam being supplied to the heating device through the supply header 14. yThe temperature within the kiln will therefore be raised to the desired amount. In' the example. shown there are three passes of heating pipes, the firstsemi or incomplete pass 13 being located in the dry end. There are therefore three transverse banks of heating'pipes in the dry end and only two in the green end of the kiln. Hence more heat issupplied to the dry end than to the green end, resulting in an increased temperature.

Inasmuch as the live steam is supplied directly to the relatively short pass 13 first, the dry end of the kiln gets the full benefit of the initiallyhot steam. Even after all of the heating` pipes down to the drain header 18 areeompletely illed with steam, there will be a temperature gradient along the steam pipes from the supply header 14 to the drain header 18. As the relatively short pass receives the steam first and is located above the remaining full length passes it will be the hottest.V T he section of full length pass 1G which is connected to the return bends 15 will be the next hottest and as this is alsolocated in the dry end it will supply a relatively large amount. of heat to the dry end.

The last section of full length pass 18, that is, the portion of these pipes adjacent the drain header 18 and extending'as far back as the region of supply header 14 are the coolest and the steam supplied to the header 14 through valve 20 can be regulated to produce a wide variation in the temperature of this section without radically varying the ratio of the heat supplied to the dry end to that supplied to the green end. Even if this section of pipe is allowed to remain substantially cool, or in other words, heated merely by the condensed steam which drains from the heating pipe sections above, a greater amount of heat is supplied to the dry end than to the green end. Hence because of this arrangement oi the heating device the temperature 'of the. atmosphere within the kiln may be varied so as to subject the lumber to different drying conditions without greatly reducing the ratio of heat supplied between the dry and green ends.

In order to appropriately support the several banks of heating pipes, cross bars 24 are provided at an appropriate spacing throughout the length of the heating pipes to the posts 10. These cross bars are lashed at their centers to the posts 10 by means of bolts 25 as shown in detail in Fig. 4. On either side of the centrally located posts 10 the pipes 24 extend underneath the beams 9 from which they are suspended by means of chains 26 (see Fig. 3). Bolts 27 are passed through appropriate lengths of the two depending portions o'f chain 26 to support the heating pipes at the desired elevations. By the use of these claniping means the desired gradient from the supply header 14 to the drain header 18 can be readily and conveniently secured. The holes in posts 1() are drilled at the proper positions by means of a hand drill and this determines the height of the cent-ers of cross bars 24. Then the chains 26 are thrown over the tops of the beams 9 and the bolts 21 are passed through the appropriate links to support the outer portions of the cross bars at the same height as the centers.

By constructing a lumber drying ap aratus in accordance with the principles o this invention, it is seen that lumber, which is progressively made to pass through the kiln, can be appropriately dried in such manner that it is simultaneously subjected to delau v nea-8,089

creasing humidity and increasing temperature.

I claim:

l. In a drying apparatus of the progressive type, means for simultaneously decreasing the humidity and increasing thek tempera ture from the entrance to the exit and ends tliereoincluding one short passat the dry end tor the initial introduction of steam and two long passes extending substantially the full length of the kiln through which to pass the steam leaving said short pass.

'2. In a drying apparatus of the progressive type, meansor simultaneously decreasing the humidity and increasing the temperature `from the entrance to the exit ends thereof including relatively short return Asteam pipes for the initial introduction or steam at the dry end connected to steam pipes leading to the Wet end and returning to the dry end. Y

3. In a drying apparatus, an elongated chamber' for the material to be dried having a heating device in the lower part thereof comprising a plurality of heating pipes eX- tending longitudinally ot the chamber, said pipes being arranged to have a plurality of passes extending the full length of the chamber and a relatively short pass located at one end of the kiln, said relatively short pass being above the other passes and being connected to the steam supply pipe so as to receive the steam before it traverses the other passes, and means for controlling the eeding of the steam to the relatively short pass. 4. In. a drying apparatus, an elongated drying Vchamber for the material to be dried having a heating device 1n the lower partv header extending cross Wise of the chamberk between the centerkof the chamber yand theV Warm end, ka drain header `extending cross Wise of the chamber at the Warm end and ylocated below the supply header, a plurality of heating pipes leading from the supply header to the Warm end of the chamber,

longitudinally of the chamber in a plurality s 'of vertically spaced passes, the uppermost pass extending for a portion only of the length of the chamber adjacent the exit end, means for supplying steam to the uppermost pass at the end thereof which is remote from the exit end of the chamber, and means for regulating the supply of steam to the heating device.

In testimony whereof I aliiX my signature.

JOI-IN BERCHMANS WELCH. 

